The number of workers aged 60 or above averaged 11.92 million in 2012, setting a record high for the sixth straight year, according to recently released government data.

The average number of elderly employees last year increased by 170,000 from 2011, accounting for 19.0 percent of the nation's total workforce, the Internal Affairs and Communications Ministry reported.

Since 2002, the ranks of elderly workers have swelled by some 3.1 million, and their presence in the total workforce increased by 5.0 percentage points. Their numbers began surging in 2007, when baby boomers born in the late 1940s began turning 60.

The increased numbers of those opting to continue working after reaching the once mandatory retirement age of 60 is a reflection of shrinking pension benefits, as well as the fact that the age at which people start to receive pensions has been raised since 2001 in response to the country's aging society and falling birthrate.

The trend is also attributed to a legal revision in 2006 that, in principle, obliges companies to continue employing those who wish to do so until age 65. Among citizens aged 60 to 64, 57.7 percent continued to work in 2012, the data showed.

Meanwhile, the number of employees aged 15 to 59 fell to 50.78 million in 2012, a plunge of around 3.7 million compared to 2002. The number of workers aged 15 to 29 plummeted by 3.2 million over the same period to 10.44 million.

The Health, Labor and Welfare Ministry has estimated that the nation's total workforce by 2030 will drop by up to 8.5 million compared with the 2010 level, unless companies increase the number of elderly and female employees on their payrolls.